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Lecture 30- The Structure of the Milky Way Galaxy Distance to the center of the globular cluster distribution: 8500 parsecs = 8.5 kiloparsecs How far is 8.5 kiloparsecs? • Let 1 au = 1cm • Nearest star (1.3 parsecs) = 2.68 km = 1.66 miles • 8.5 kiloparsecs = 17,532 km = 10,870 miles (2.74 Earth radii) • Light signal transmitted from the GC would take 27,700 years to reach us Where (on the sky) is the galactic center? In Sagittarius RA = 17h45m DEC=-28.3 degrees Position on SC1 Chart Location on Sky of Galactic Center At radio wavelengths, we can see to the galactic center. Interstellar dust has very little effect on radio waves The Galactic Center Lang, Lazio, et al At the Very Center What do we see at the galactic center (radio and infrared wavelengths? • Strong radio source (synchrotron radiation) • At infrared wavelengths, can see stars orbiting very vast around Sgr A • http://antwrp.gsfc.nasa.gov/apod/ap001220. html • Ten years of observations speeded up The Orbit of Star S2 Star S2 passes about as close to Sagittarius A* as the planet Pluto passes to the Sun. Indicates supermassive object in a very small region Andrea Ghez paper
